Category

Published on

24 Mar 2016

Abstract

CNTFET can currently simulate the impact of quantum mechanical size quantization and phase coherence in zigzag nanotubes with both planar and coaxial exterior architectures. The application is based on the Non-Equilibrium Greens’ Function (NEGF) techniques using a pz-orbital nearest-neighbor tight binding. Full three-dimensional (3D) electrostatics has been captured by the Finite-Element-Method (FEM) of solving the Poisson Equation. Solution of this set of equations is computationally expensive. One can reduce the simulation time by using a mode-space approach instead of the real-space approach. By default the simulator solves for both electrons and holes, although one may activate electron-transport only. The numerical problem consists in computing the diagonal elements of the matrix Gr = [ EI - H - ∑ ]-1 (retarded Green’s function) and G< = G∑<G† (electron correlation Green’s function), where E is the energy level, H is the device Hamiltonian matrix, and ∑ and ∑< are self energies († denotes the transpose conjugate of a matrix). The algorithmic flow is based on Dyson’s equation solved through recursive Green's function approach. Developed at Purdue University, CNTFET has been parallelized with Message Passing Interface (MPI) and ported to various computing platforms. The MPI is applied in the integration procedure to calculate the charge density over the energy spectrum while the Green’s function at each energy point is calculated by a serial algorithm.